Gene-Testing Machine for Doctors

Gene-Testing Machine for Doctors

Simple testing: This disposable cartridge can detect genetic variations from blood samples. The circles lining the top and bottom are loaded with reagents for different chemical reactions. DNA is isolated from white blood cells and captured on a glass slide within the cartridge.

A desktop instrument recently approved by the U.S. Food and Drug Administration might finally bring pharmacogenomic testing–the use of a patient’s genetic information for drug prescription decisions–to the mainstream. The device, made by Nanosphere, a startup based in Northbrook, IL, can, in a matter of hours, detect genetic variations in blood that modulate the effectiveness of some drugs. Dubbed Verigene, the technology employs a combination of microfluidics and nanotechnology, housed in a single plastic cartridge, to pull DNA from a blood sample and then screen it for the relevant sequences.

“We believe the benefit of our system is that this simple cartridge format could be run in any hospital, even a doctor’s office,” says William Moffitt, chief executive at Nanosphere. “We’re moving complex testing to the point of patient care.” Moffitt says Verigene is the first nanotechnology-based microfluidics product capable of analyzing DNA directly from a blood sample.

People can respond to drugs very differently, thanks in part to commonly occurring genetic variations in enzymes that metabolize some of the mostly highly prescribed compounds, such as heart medicines, pain medicines, and antidepressants. While doctors have widely adopted pharmacogenomic testing for prescribing some cancer drugs, such testing hasn’t yet taken hold for many other drugs whose effectiveness is modulated by genetics, including those for HIV, pain control, and epilepsy. The technology needed to detect these variations in patients has been available for years, but the process is often time-consuming and expensive. Physicians typically must send patients’ saliva or blood samples to a central lab, where the DNA is isolated, amplified, and analyzed. That process can take days or weeks.

“In some cases, it doesn’t matter if it takes a week to get a result. But in some cases we would like to have the information to choose a drug during the office visit, when the patient is right there,” says Howard McLeod, director of the Institute for Pharmacogenomics and Individualized Therapy at the University of North Carolina, Chapel Hill. “That way we can say, this drug is the one your DNA says will most likely be beneficial.”

The anticoagulant warfarin, for example, is frequently prescribed to prevent blood clots. But people metabolize the drug differently, meaning patients must be carefully monitored to make sure they don’t suffer dangerous bleeding. The FDA changed the drug’s label in 2007 to note that two specific genetic variations affect a patient’s sensitivity to the drug, but broad gene testing has not yet caught on. “Currently, available genotyping tests for warfarin pharmacogenomics require isolation of DNA from blood and testing in a molecular diagnostics laboratory certified for high-complexity testing,” says Karen Weck, director of the molecular genetics laboratory at the University of North Carolina, Chapel Hill.

Nanosphere is developing a test that can detect these variations in blood samples in an hour or two. A patient’s blood is injected into a disposable cartridge, which holds a glass slide dotted with DNA. The plastic frame also houses a system of microfluidics chambers containing the reagents for a number of chemical reactions. When the cartridge is inserted into the Verigene instrument, mechanical valves and air pressure mix the reagents in different chambers, triggering a series of reactions.